JSFiddle - React, Tailwind, and code Playground
by lonewolfs
HTML
<div id="container1">
Container1
<div id="out" class="in">
Container2
<div id="container3" class="in">
Container3
</div>
</div>
</div>
CSS
div{border:thin solid #F00;}
#container1{width:auto;margin:10px;height:auto;}
#container2,#out{width:auto;margin:10px;height:auto;}
#container3{width:auto;margin:10px;height:25px;}
.b{color:#999;}
#out .in{background-color:#F00;}
JavaScript
$('#container2').addClass('b');